Diesel Engine vs Petrol Engine: The Definitive Guide.


by Contributor

Photo: Life-Of-Pix, Pixabay, License

(Feb. 17, 2020) — Debates between diesel engine users and petrol engine users are commonplace, especially among automobile lovers. Although personal preferences and mode of use play a huge role in the perceptions of either, ardent users swear that one trumps the other ultimately.

The debates are as old as the engines themselves. However, they have become more commonplace because of the proliferation of diesel-powered cars. Diesel engines were traditionally exclusive to trucks and other heavy-duty automobiles. Recent innovations, however, have changed the narrative, making them direct competitors.

Similarities between Diesel and Petrol Engines

Interestingly, diesel and petrol engines are very similar, especially in theory and function. As everyone knows, the engine of a car is like a heart that keeps it working. It is responsible for the production of energy that produces motion for the vehicle. In that regard, both engines function precisely the same.

Theoretically too, they are both internal combustion engines and rely on the burning of fuel to produce energy. Internal combustion engines use either two or four-stroke cycles to generate power. Two-stroke engines are, however, used less and less in modern times.

A four-stroke cycle consists of the following phases:

  • Intake phase: air goes into the cylinder through the intake valves.
  • Compression phase: the air is compressed after the closure of the intake valves and mixed with fuel.
  • Power phase: an explosion is caused by the ignition of the air and fuel mixture. This explosion causes a downward movement of the piston, which in turn causes motion in the crankshaft.
  • Exhaust phase: here, the air-fuel mixture is removed from the engine cylinder through an exhaust valve

Critical differences between Diesel and Petrol Engines

The first, immediately obvious, difference between both engines is the fuel used to operate them. The diesel engine makes use of diesel while petrol engines make use of gasoline. Both fuels are products of crude oil but differ significantly. Diesel is more viscous than gasoline owing to its chemical composition. It also has a very distinct smell. One of the reasons for the growing popularity of diesel cars is that diesel itself contains more energy per litre than gasoline.

However, the more remarkable difference between diesel engines and petrol engines is in the third phase of the four-stroke cycle – power. Petrol engines typically make use of a spark plug to ignite the compressed fuel-air mixture. In diesel engines, on the other hand, there is no spark plug. The heat of the compressed air instead is used to ignite the fuel. This method of ignition is based on the two factors – the compression ability of diesel and its high energy content. The combination of both factors means that when brought in contact with compressed(heated) air, diesel is very likely to ignite.

Interestingly, the air-fuel mixture is carried out within the container in a diesel engine. This is as opposed to traditional petrol engines that mix the air and fuel in a carburetor before feeding it into the cylinder.

These seemingly simple differences make for very different performance levels from both engines and divide the automobile world as you will see.

Which engine edges the other?

The arguments for or against either type of engine is rooted in the performances and weaknesses of one as opposed to the other. So, we will consider both sides of the argument:

The case for diesel engines

The minor alteration in the setup of diesel engines allows for a more considerable amount of power to be produced. Since the air and fuel undergo mixture and combustion inside the cylinder, there is less chance for fuel wastage. The addition of direct fuel injectors to diesel engines better enhances power production even more.

You can check out fuel injector models here: https://goldfarbinc.com/collections/fuel-injection-pump-new-used-rebuilt.

Also, recent progress with turbochargers has made it possible to reduce the wasted energy in a diesel engine further. It does this by trapping heated gases in the exhaust and using it to force more compressed air into the combustion chamber. This also leads to cleaner emissions from diesel engines.

Diesel engines also require less maintenance than petrol engines despite costing more on average per session.

There is also the argument for the fuel itself. Diesel produces more energy per litre than gasoline, is less volatile and is also cheaper in most countries.

The case for petrol engines

The first advantage of petrol-engine cars is that they are cheaper to buy. While some people argue that the overall cost of owning a diesel-powered vehicle is less eventually, the initial cost favours petrol engines. Diesel engines are more complicated and expensive to build, and that is reflected in the pricing. In addition to that, maintenance for fuel engines cost significantly less than that of diesel for the same reasons.

The heavy machinery in diesel engines also causes a noticeable noisiness about them. This can be very frustrating to deal with. Fortunately, petroleum engines do not have this problem. They run smoother and with less noise.

Petrol engines are also typically faster than diesel engines. They produce more horsepower and accelerate faster. However, this may no longer be the case with all diesel engines as newer versions are coming out with turbochargers and other speed enablers.


Choosing between a diesel-powered vehicle or a petrol engine boils down to personal preference and need. If you are using your car to do the heavy-duty lifting, then you are better off using a diesel-powered engine.

The distance you have to drive should also affect your choice. Fuel efficiency on diesel combustion may not be evident at smaller distance measurements. So, unless you’re doing a lot of long-distance travelling, a petrol engine may be the best for you.

It would be best if you also considered the resale proposition of your car. Diesel cars are generally believed to be more durable than petrol cars because of their stronger engines. As such, diesel engine vehicles have a higher resale value in comparison.

Making a decision on whether to get a diesel engine and a petrol engine is rather far from a zero sum affair. Given the advancements in automobile technology, you will not be missing out on too much regardless of your choice.

One Response to "Diesel Engine vs Petrol Engine: The Definitive Guide."

  1. Rattlerjake   Tuesday, February 18, 2020 at 4:03 AM

    Lets not forget to add that some diesel engines can also run on waste oil, vegetable oil, and/or black diesel (mix of waste oil or veg oil and diesel). Because these fuel sources are usually FREE, it can make operating cost considerably lower; just requires filtering.

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